A hand-held ophthalmoscope is modified by replacing or augmenting the focusing wheel with a manual or automatic focusing lens system which provides coarse and fine focus. In one embodiment, an imager, such as a CCD array or video camera, is placed optically conjugate to a viewing screen analogous to that used in single lens reflex (SLR) cameras such that focus operations performed by the examiner to adjust the fine focus of the image on the viewing screen also fine focuses the image on the CCD array or video camnera. The viewing screen can also incorporate a focusing aid such as, but not limited to, microprisms.
In this embodiment, the invention operates by using an optical system which includes a straight path from the patient""s eye to the viewing screen with a beam splitter interposed to cause the image of the patient""s eye to be reflected onto the CCD array or video camera while the image is also passed through onto the viewing screen. As a result, when the examiner uses the focusing lens system, manual or automatic, positioned between the beam splitter and the patient""s eye, to affect the image seen on the screen, the focus of the CCD array or video camera is simultaneously affected as well.
In an alternate embodiment the image from the CCD array is sent to a liquid crystal display (LCD) which is substituted for the viewing screen. The examiner, who does not directly view the patient""s eye, focuses the image on the LCD which automatically and simultaneously focuses the image output from the CCD array.
In still another embodiment a novel automatic focusing system, focuses the output of the CCD array independently of the examiner.
The image on the CCD array can be output in digital or analog form. If a video camera is used, the image is output in standard (analog) video format.
Several objects and advantages of the present invention are:
(a) to eliminate the examiner""s accommodation as an adjustable optical element other than to bring the real image on the viewing screen into sharp focus;
(b) to provide an ophthalmoscope that assures that the CCD or video camera image is in fine focus; and
(c) to provide an ophthalmoscope that has an image capture switch, thus allowing the examiner to save the in-focus image that is directly viewed through the ophthalmoscope.